build: Allow product to override debug defconfig

Falcon GPE has a requirement that userdebug builds must have high
performance.  Allow GPE product to override the use of debug
options inherited from the common kernel.

Change-Id: I3b7ed452c5424719da65640ced5656073599a918
Reviewed-on: http://gerrit.pcs.mot.com/590151

Tested-by: Jira Key <jirakey@motorola.com>
Reviewed-by: Dmitry Sokolov <dima@motorola.com>
SLTApproved: Dmitry Sokolov <dima@motorola.com>
Submit-Approved: Dmitry Sokolov <dima@motorola.com>

defconfig.mk

@@ -6,10 +6,12 @@ KERNEL_DEBUG_DEFCONFIG          := $(LJAPDEFCONFIGSRC)/debug-$(subst _defconfig,
 
 # add debug config file for non-user build
 ifneq ($(TARGET_BUILD_VARIANT), user)
+ifneq ($(TARGET_NO_KERNEL_DEBUG), true)
 ifneq ($(wildcard $(KERNEL_DEBUG_DEFCONFIG)),)
 PRODUCT_SPECIFIC_DEFCONFIGS += $(KERNEL_DEBUG_DEFCONFIG)
 endif
 endif
+endif
 
 # append all additional configs
 ifneq ($(KERNEL_EXTRA_CONFIG),)